Energy-Related Carbon Dioxide Emissions 

figure data

Absent the application of CCS technology (which is not expected to come into use without changes in current policies that are not included in the reference case), CO2 emissions from the combustion of fossil fuels are proportional to fuel consumption and carbon content, with coal having the highest carbon content, natural gas the lowest, and liquid fuels in between. In the AEO2008 reference case, the coal share of total energy use increases from 23 percent in 2006 to 25 percent in 2030, while the share of natural gas falls from 22 percent to 20 percent, and the liquids share falls from 40 percent to 37 percent. The combined share of carbon-neutral renewable and nuclear energy grows from 15 percent in 2006 to 17 percent in 2030.

Taken together, projected growth in the absolute level of primary energy consumption and a shift toward a fuel mix with slightly lower average carbon content cause projected energy-related emissions of CO2 (Figure 8) to grow by 16 percent from 2006 to 2030—slightly lower than the projected 19-percent increase in total energy use. Over the same period, the economy becomes less carbon-intensive, because the 16-percent increase in CO2 emissions is about one-fifth of the projected increase in GDP (79 per-cent), and emissions per capita decline by 5 percent. In the AEO2008 reference case, projected energy-related CO2 emissions grow from 5,890 million metric tons in 2006 to 6,851 million metric tons in 2030. By comparison, in the AEO2007 reference case, energy-related CO2 emissions were projected to grow by about 35 percent, to 7,950 million metric tons in 2030, reflecting both a higher projection of overall energy use and, to a lesser extent, a different mix of energy sources.